Alloy and method of working and heat treating the same



Patented Sept. 24, 1929 UNITED STATES PATENT OFFICE MICHAEL e. 0038011, or JACKSON HEIGHTS, NEW YORK, assmnon To ELECTED METALLURGICAL COMPANY, A c

ORPORATION OF WEST VIRGINIA ALLOY AND METHOD OF WORKING AND HEAT TREATING THE SAME Ru Drawing.

The invention relates to copper-silicon.

alloys and to certain processes of working and heat-treating such alloys. My researches indicate that the increase in the general chemical resistance of a metal as achieved by alloying depends mainly upon the substitution of the atoms of the base metal in its crystals by atoms of an added element which in itself has a marked resistance to chemical corrosion, and in general the larger the number of the atoms substituted the higher the corrosion resistance of the alloy under consideration.

Silicon is one of the few elements dis- 5 playing a strong corrosion resistance of its own and in a number of cases the addition of silicon to another metal gives a corrosion resistant product.

Herctofore numerous made to use silicon as an alloying element to increase the resistance of copper to attack by corrosive agents, and at the present time a copper-base alloy containing as much as 3.5% silicon is being manufactured. Theoretical considerations would tend to indicate that the corrosion resistance of copper-silicon alloys could be increased by increasing the silicon content. However, copper alloys containing more than 3.5% silicon, when worked according to the procedure usually followed in working alloys containing 3.5% silicon or less, show physical properties markedly in- -ferior to those exhibited by the alloys last mentioned. This fact is brought out by the following comparisons of the properties of the 3.5% silicon alloy with those of a 5% silicon alloy when worked in the usual manner.

1. An alloy with 3.5% silicon if rolled. annealed and further cold rolled will show 120,000 lbs. per square inch ultimate strength with 6% elongation in 2 against 60,000 lbs. and 60% elongation in the annealed state. Therefore, the annealed metal can be cold worked extensively for the purpose of making useful industrial articles.

2. An alloy with 5% silicon if rolled and annealed in the usual manner will show 07,000 lbs. ultimate strength with elon gation in 2": If, however, cold rolled furefforts have been Application. filed October 4, 1926. Serial No 189,557.

ther to say reduction, it shows only 60,000 lbs. ultimate strength and no ductility whatsoever.

- 3. An alloy .with 3.5% silicon if properly annealed (for instance by treating the cold rolled material for 1 hour at 700 C.) shows uniform clear crystals having good properties as respects resistance to selective corrosion.

4. An alloy with 5% silicon if annealed and'furnace or air cooled shows striated crystals' which tarnish and corrode much quicker than those of the 3.5% silicon alloy.

As a result ofmy investigations, come to the following conclusions respecting these phenomena:

(a) The limit of solid solubility at room temperature and up to about 500 C. is found at 3.7% silicon and not at 5% as has been prezvgiously suggested. 6 with temperature until it lies at 6.7% at 800 C.

(a) The striation of the crystals of the annealed 5% silicon alloy or of any other above 3.7%silic'on is due to the formation of parallel rows of tiny precipitated grainlets of a secondary constituent probably a compound of the formula Cu Si.

(d) Quenching from a temperature well above that at which this precipitation starts to take place leaves the-crystals clean, free of striation, and free of the tarnishing and accelerated corrosion effects.

For example, I have found that an alloy containing 5% silicon hot rolled at 700- 750 C. and quenched from 700 C. can be cold rolled easily and attains 130,000 lbs. strength with 5% elongation after a reduction of As another example, 6.5%. able at a tempefhture of forged or rolled and then quenched from 7 50- 800 C. it shows 70,000 lbs. strength with 30% elongation and has good corrosion resistance. Moreover, while this alloy in the cast state has substantially no impact resistance, it will possess an impact resistance of 8 ft. lbs. (Izod test) if heat treated for 6 hours at w an alloy containing silicon has been found to be fully work- 720820 C. If hot The limit of solid solubilityincreases I have 800 C. and quenched. If hot Worked and quenched from a tem erature of 750-800 C. it shows 24 ft. lbs.

belonging to the socalled alpha solid solution phase are free from striation.

My invention is based upon the following discoveries (1) That at temperatures above 500 0., the actual range depending on the composition,copper-silicon alloys containing above 3.7% silicon and below 6.7% silicon represent homogeneous compositions fully and commercially workable.

(2) That this homogeneous state can be preserved by quenching from suitable temperatures, yielding a material tilit-y even with 6.5% silicon present.

(3) That cold work does not impair the properties of these quenched compositions a That copper-silicon alloys containing from 37-67% silicon and Worked and heat treated according to the present invention are characterized by high resistance to corrosion.

As a specific embodiment of the method as applied to the manufacture of articles for industrial uses from copper-silicon alloys falling Within the present invention, I set forth below a preferred procedure to be followed in making a spun kettle of 6.5% silicon alloy:

(a) A melt is made of the desired composition in the usual way. The molten copper may be preferably deoxi-dized with magnesium and the melt may contain in addition to silicon small amounts of tin (up to 2%) or zinc (up to 5%) or of aluminum (up to 3%).

(b) The melt is poured in a mold to yield a plate ingot of about 2 inches thickness.

(0) The ingot is kept in a furnace at approximately 7 C. for 12 hours and next at 780 Cjfor 3 hours.

. ((Z) The ingot is hot forged to 1 inches to eliminate ingotism and nest hot rolled to the desired thickness. Care is taken not to allow the temperature of the metal to go above 820 C. or to fall below 720 C.

((1) The rolled sheet is placed kept at 750-800 G. for l hens: in Water.

(f) The cold sheet is pickled.

(g) The spinning operai n begins and alternates with frequent annealing at750- 800 C. followed by quenching.

It is to be understood that the invention is not limited to the precise temperatures and manipulations set forth above and that Various modifications in the in a furnace and quenched zod. In the quenched state it is fully homogeneous and its crystals of high duos procedure outlined metals of the iron group, except such amounts of iron as may be introduced as an impurity with silicon during the alloying operation, are preferably excluded.

claim:

1. Process of changing certain of the physical characteristics of copper-base alloys (.Oltfillllllg silicon in the range of 3.7% to 7m treatment at a temperature of approximately 500 to 800 C. to secure a homogeneous composition of copper and silicon which Will be supersaturated at room temperature and thereafter quenching the alloy from a temperature within the range above-mentioned to preserve such condition of solid solution.

2. Process of working copper-base alloys containing from 3.76.7% silicon, comprising homogenizing the cast alloy, hot Working it, and preserving its homogeneity by quenchmg.

3. Process of working copper-base alloys containing from 3.7-6.7 silicon, comprising homogenizing the cast alloy, hot'working it, preserving its homogeneity by quenching. and then subjecting the alloy to cold working.

41:. Processv of Working copper-base alloys containing 3.76.7% silicon, comprising heating the-cast alloy at a temperature of 500 800 C. until a homogeneous structure is obtained, hot working the alloy at a temperature above 500 0., and quenching from a temperature above 500 C.

- 5. Process of Working copper-base alloys containing3.7% to 6.7% SlllCOD, comprising Working the cast alloy at a temperature upwards of 700 (3., and then quenching from a temperature upwards of 700 C.

6. Process of Working copper-base alloys containing 3.7% to 6.7 0 silicon, comprising homogenizing, hot working and quenching alloy, all at a-temperature above 700 0., said quenching treatment being followed by cold Working.

7. Process of working copper-base alloys containing approximately 6.5% silicon, comprising heating the cast alloy at a temperature of 720-820 (1, working the alloy at a temperature above 720 0., and. then quencln ng from a temperature of 750--800 C.

- In testimony whereof, I afiix my signature. ltlIOHAEL G. COESON.

may be made Without departing from the scope of the invention.

While the invention has particular applicability to a binary alloy of copper and silicon, small amounts of certain other elements may be present. Among these are tin, zinc and aluminum above-mentioned. However,

comprising subjecting the metal to heat i 

